Patient interface for spectroscopy applications

ABSTRACT

A patient interface and a method of installing a patient interface for a spectroscopy kit on a patient. The patient interface includes a butterfly-shaped patient interface with a cap on top of the patient interface and in proximity to an optical head.

CLAIM OF PRIORITY

This application is a continuation-in-part of application Ser. No.11/129,935, filed May 16, 2005, and claims the benefit of applicationSer. No. 60/790,462, filed Apr. 7, 2006, both entitled “PATIENTINTERFACE FOR SPECTROSCOPY APPLICATIONS.”

BACKGROUND OF THE INVENTION

The present invention relates to the field of medical spectroscopy andmore specifically to the field of mounting sensors on a patient for usein spectroscopy.

The use of spectroscopy in medical condition diagnosis has becomecommonplace. Typically, light is placed on the surface of tissue in onelocation and transmitted or scattered light is collected from the tissuein another location. A spectral analysis of the collected light is thenperformed and the results are compared to stored information aboutspectral profiles of tissue having known conditions. From thiscomparison, the condition of the tissue under study may be determined.

The light to be transmitted into the tissue is typically placed on thetissue through use of an optical head. The same optical head may be usedto collect the light. Some spectroscopy systems allow for collection oflight that passes through tissue and therefore one optical head is usedfor light transmission while a second optical head is used forcollection.

The optical head may be held directly on the tissue by a doctor, nurseor technician, it may be directly taped or strapped into place, anexternal structure may hold it in place or it may be held securely inplace through a patient interface. A patient interface is a speciallydesigned structure that will typically hold the optical head within itsstructure and includes an adhesive, suction, compressive, strapping, orother (e.g. glove like) structures to hold the patient interfacesecurely to the patient's tissue. Some examples of patient interfacesare shown in U.S. Pat. Nos. 4,223,680, 4,537,197, 4,653,498 (the “New”patent), 4,817,623, 4,825,879 (the “Tan” patent), 4,830,014 (the“Goodman” patent), 4,865,038 (the “Rich” patent), 4,964,408 (the “Hink”patent), 5,094,240, 5,111,817 (the “Clark” patent), 5,224,478,5,267,563, 5,402,777, 5,584,296, 5,879,373 and 6,381,489.

It has been found that performing blood spectroscopy on the fingersallows for access to a significant quantity of blood vessels that arenear the surface of the skin. Accordingly, a number of patents have beendirected to such patient interfaces mountable on a finger, such as theNew, Tan, Goodman, Rich, Hink and Clark patents.

A problem with spectroscopy of fingers is that the patient interfaces orthe attachment straps tend to wrap entirely around the finger. Bloodflow to the finger can be thereby restricted and this can affect theaccuracy of the spectroscopy.

Further, some locations on the body present more blood vessels near thesurface than others. Even within a short range of a location thatprovides a reasonable level of blood vessels for measurement, a betterlocation may exist. However, the prior art suffers from an inability torelocate the sensor easily once the sensor has been affixed to thetissue.

SUMMARY OF THE INVENTION

The present invention is a device and process for assisting in locatinga fixture for measurement of an attribute of tissue, such as thepercentage of oxygenated hemoglobin present in the tissue. In oneembodiment, a fixture for holding a light source and a light path to asensor or the sensor itself includes a base approximately shaped to athenar muscle of a hand, the base including a passage for lighttransmission and collection therethrough. A first wing portion isconnected to the base. The first wing portion may be partially wrappedaround a body part when the fixture is in use. A second wing portionconnected to the base whereby the second wing portion may be partiallywrapped around the body part in an opposite direction from the firstwing may also be included. The fixture may also include a concave regionformed between the two wings for providing a locating feature for thefixture.

In another embodiment, a patient interface for a tissue measurementinstrument, includes an elongated, flexible base member having a firstrounded end and a second rounded end. The base member has a passage forlight transmission therethrough. A first wing extends from the secondend for partially wrapping around a body part to which the interfacewill be attached. The patient interface may include first and secondends that are convex rounded ends. The patient interface may furtherinclude a second wing extending from the second end and first and secondconvex regions extending from the first end. Alternatively, the firstend of the patient interface may have a convex rounded end while thesecond end is a concave rounded end. In still another alternative, thepatient interface has a second wing extending from the second end.

In yet still another alternative embodiment, the base member includesfirst and second holes allowing for light transmission therethrough. Alight source is provided for providing light to pass through the firsthole while a light path (such as an optical fiber) is aligned with thesecond hole for collecting light that has passed through tissue andadapted to transmit a signal representative of the collected light.

In still another embodiment, the patient interface has a longitudinalaxis between the first rounded end and the second rounded end and thefirst and second holes lie substantially on the longitudinal axis.

The patient interface has a top and bottom side. In an embodiment, thebottom side is adapted to be placed in contact with the patient, and anadhesive is located on the bottom side while a first liner is used tocover the adhesive. In a variant to this embodiment, a second liner maybe used in conjunction with the first liner. The first liner then coversa first portion of the adhesive while the second liner covers anotherportion of the adhesive.

In yet another embodiment of the patient interface, a structure foraiding in the measurement of an attribute of tissue includes a basehaving a concave locating feature and a longitudinal axis thatsubstantially bisects the locating feature and send and receive fiberseach having ends, the ends lying in a line generally along thelongitudinal axis and being substantially coplanar when in use.

Another embodiment includes a base having a concave locating feature anda longitudinal axis that substantially bisects the locating feature andsend and receive light ports generally along the longitudinal axis, thesend and receive light ports being substantially coplanar when in use.

One more embodiment contains a base having a concave locating featureand a longitudinal axis that substantially bisects the locating featureand an elongated opening lying generally along the longitudinal axis,the elongated opening lying generally in a plane when in use.

The invention also is a method of locating a patient interface for atissue measurement instrument on a patient. Typically, the patientinterface has a measurement side with a light transmission hole and alight receipt hole. The process includes the steps of moving the patientinterface around on the tissue in a particular region of the body untila desired threshold reading is achieved on the tissue measurementinstrument. Then, upon finding the location where a desired thresholdreading is achieved, temporarily placing the patient interface to thepatient for a predetermined amount of time and finally affixing thepatient interface to the patient. The process may also include the stepsof generally aligning the light transmission hole and the light receipthole along one of a adductor pollicis, a thenar eminence, a hypo thenareminence, a digit, a first dorsal interosseous or a deltoid muscle.

In another process for attaching the patient interface to a patient, forlocating a tissue measurement instrument on a patient the processincludes moving the patient interface around on the tissue in aparticular region of the body until a location where a desired thresholdreading is achieved on the tissue measurement instrument is found. Then,upon finding the location where a desired threshold reading is achieved,the patient interface is firmly held to the patient. Then, the patientinterface is partially removed from the patient while holding it inplace so that a first amount of adhesive on the measurement side of thepatient interface may be readied for attachment to the patient. Next,the first amount of exposed adhesive is placed on the patient. Then, thepatient interface is partially removed in a second direction so that asecond amount of adhesive may be readied for attachment to the patient.Finally, the second amount of exposed adhesive is placed on the patient.In additional steps to this process, the first amount of adhesive isactivated by removing one of the first and second liners; and the secondamount of adhesive is activated by removing the other of the first andsecond liners.

In still another embodiment, a method of locating a patient interfacefor a tissue measurement instrument is described. The patient interfaceincludes an elongated, flexible base member having a first rounded end,the base member having a passage for light transmission therethrough andat least first and second wings extending from the first end each forpartially wrapping around a body part to which the interface will beattached wherein the first end is a concave end. The method of placementincludes locating the concave end generally transverse the shoulderaxially aligned with the deltoid. The patient interface is then affixedto the patient.

In further steps to this process, the patient interface can include anadhesive on a patient facing surface and a split liner can be used tocover the adhesive until the patient interface is to be affixed to thepatient. The process then includes the further steps of lifting a firstportion of the patient interface from the patient; removing a firstpiece of the split liner, placing the first portion of the patientinterface back on the patient, lifting a second portion of the patientinterface from the patient, removing a second piece of the split liner,and placing the second portion of the patient interface back on thepatient.

There is yet one more process for locating the patient interface on apatient, where the patient interface has a generally concave locatingedge and a measurement side with a light transmission hole and a lightreceiving hole aligned generally along an axis bisecting the concavelocating edge. The process includes the steps of locating the concavelocating edge proximate the base of a digit and aligning the lighttransmission hole and the light receiving hole along a major musclegroup to be measured.

Yet another structure for aiding in the measurement of an attribute oftissue includes a base having a patient side and an adhesive on thepatient side, the adhesive having at least first and second adhesiveregions. A split liner having first and second portions covers the firstand second adhesive regions respectively. The first portion has a firstadhesive facing region attached to the adhesive, a first hinge region, afirst patient facing region connected to the first adhesive facingregion through the first hinge region and a first tab extending beyondthe base. The second portion has a second adhesive facing regionattached to the adhesive, a second hinge region, a second patient facingregion connected to the second adhesive facing region through the secondhinge region and a second tab extending beyond the base. A method ofplacing such a patient interface includes the steps of placing a base ona patient. The base has a patient side and an adhesive on the patientside. The adhesive has at least first and second adhesive regions. Asplit liner having first and second portions covers the first and secondadhesive regions respectively. The first portion has a first adhesivefacing region attached to the adhesive, a first hinge region, a firstpatient facing region connected to the first adhesive facing regionthrough the first hinge region and a first tab extending beyond thebase. The second portion has a second adhesive facing region attached tothe adhesive, a second hinge region, a second patient facing regionconnected to the second adhesive facing region through the second hingeregion and a second tab extending beyond the base. The first and secondportions meet to form a separation. A user pulls on the first tab in adirection substantially normal to the separation and pulls on the secondtab in a direction substantially normal to the separation. In anotherembodiment of a patient interface the patient interface includes aflexible base member having a pair of opposing wings extending from acentral region of the base member, each wing having a convex outerperimeter and generally symmetric about the central region and forpartially wrapping around a body part to which the interface will beattached. The base member having a passage for light transmissiontherethrough and a cap positioned on the central region of the basemember and in proximity to an optical head.

In yet another embodiment, a patient interface includes a flexible basemember having a central region along a longitudinal axis and pair ofopposing wings extending from the central region, each wing having aconvex outer perimeter and generally symmetric about the longitudinalaxis, each of the wing for partially wrapping around a body part towhich the interface will be attached; the base member having a passagefor light transmission therethrough; and a cap positioned on the centralregion of the base member and in proximity to an optical head.

Another embodiment of invention is a method of installing a patientinterface for a tissue measurement instrument that includes the steps ofproviding a flexible base member having a pair of opposing wingsextending from a central region of the base member, each wing having aconvex outer perimeter and generally symmetric about an axis that issubstantially perpendicular to a longitudinal axis, and for partiallywrapping around a body part to which the interface will be attached; thebase member having a passage for light transmission therethrough; a cappositioned on the central region of the base member and surrounding anoptical head. Then one end of a cable is connected to the optical headand the other end of the cable is connected to a monitor and finally thepatient interface is affixed.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of a patient interface of the presentinvention.

FIG. 1A is a slice view taken along line 1A-1A of the patient interfaceshown in FIG. 1.

FIG. 1B is a bottom view of the patient interface in FIG. 1.

FIG. 1C is a side view of the patient interface of FIG. 1 furtherincluding an adhesive layer and a release liner layer.

FIG. 1D is a bottom view of the patient interface of FIG. 1 with a splitliner.

FIG. 1E is a bottom view of the patient interface with a single pieceliner.

FIG. 1F is a bottom view of an alternative embodiment of the patientinterface with a single elongated hole.

FIG. 1G is bottom view of an alternative embodiment of the patientinterface with a single circular hole.

FIG. 2A is a top view of a second embodiment of the patient interface.FIG. 2B is a bottom view of the second embodiment of the patientinterface.

FIGS. 3A-C are perspective views of a patient interface being placed ona hand.

FIGS. 4A-B are a flow charts of two processes for placing the patientinterface.

FIGS. 5A-D are perspective views of an alternative placement of thepatient interface of FIGS. 2A-B.

FIGS. 6A-B show an alternate placement of a patient interface proximalto the adductor pollicis.

FIGS. 7A-B are top and bottom views of yet another embodiment of thepatient interface.

FIGS. 8A-B are top views of two additional interface designs where anoptical head may be plugged into the interface.

FIGS. 9A-B are a top view of interface locations on the back of thefirst dorsal interosseous between the finger and thumb and thehypothenar respectively.

FIG. 10 is an elevation view of a patient interface on a patient'sdeltoid muscle.

FIG. 11A is a bottom perspective view of a patient interface with analternative liner. FIG. 11B is a top expanded slice view along line11B-11B.

FIG. 12 is a top perspective view of yet another embodiment of thepatient interface also showing an optical head.

FIG. 13 is a slice view of the patient interface and optical head ofFIG. 12.

FIG. 14 is an expanded view detailing the layers of the patientinterface as shown in FIG. 13.

FIG. 15 is a top view of a spectroscopy kit according to anotherembodiment of the invention.

FIG. 16 shows cross-sectional and schematic views of the optical head,cable and connector of FIG. 15.

FIG. 17 shows top, perspective, end and side views of the optical headof FIG. 15.

FIG. 18 shows top and side views of the patient interface of FIG. 15.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, thereshown is a patient interface 10 for usewith a tissue spectrometer (not shown). The patient interface includesbase 12, wings 13 and 14, convex regions 15A and B, concave region 16,pocket 18 and opening 20. The base 12 may have a semi-circular portionbetween points A and B and extend in convex regions 15A and B. Theconvex regions are intended to engage peripheral portions of the thenareminence or other sites when positioned for use on the hand. The convexregions are also intended to shield ambient light while engaging theperipheral portions of the thenar eminence. The convex regions 15A and Blead into concave regions 17A and B which are intended to roughly followthe narrowing of the thenar eminence or other sites at its distal end.Wings 13 and 14 are for partially wrapping around the thumb or othersites of the patient. Concave region 16 serves as a locating featuresuch as at the base of the thumb or other finger or a pediatric shoulderfor example. Other locating features such as v shapes or notches arealso contemplated. Concave region 16, located between the wings, isintended to engage the patient's thumb approximately at the intersectionof the first metacarpal bone (or the other metacarpal bones) with thehand.

Alternatively, the present patient interface can be used forspectroscopy applications on baby or small child in the deltoid regionof the child's arm as shown in FIG. 10.

The bottom of the patient interface (FIG. 1B) shows an essentially flatpatient surface 22 with holes 23 and 24 therein. Hole 24 is preferablyfor light transmission into the patient while hole 23 is for collectinglight from the patient into a return transmission to the spectrometer.The holes, particularly hole for receiving light is preferably locatednear the center of the convex region so that additional shielding fromambient light is provided. As can be seen in the slice view FIG. 1A,opening 20 provides a path for fiber optic cable 28 to reach the insideof pocket 18. There, a light transmission fiber 30 is provided with apath to transmit light to the patient. Here, fiber 30 terminates andlight exits the fiber and is reflected through hole 24 by mirror 26.Light returning from tissue (not shown) is collected through hole 23into light return fiber 29 for transmission to the spectrometer foranalysis. In one embodiment, the holes 23 and 24 are at leastapproximately co-axial with an axis 19C extending between a centerpoint19A of the concave region 16 and a centerpoint 19B of first end 11. Inanother embodiment, a mirror is positioned inside the opening to reflectlight onto a receive fiber. It should be noted that while one preferredembodiment has been described, there are many other possible methods oftransmitting light to tissue and collecting and transmitting the returnlight signal back to the spectrometer.

In an alternative embodiment, a single elongated hole 23A is used toreplace holes 23 and 24. In such an embodiment, an integrated sensorhead may be used to hold light transmission and light receiving paths inplace and to isolate the light receiving path from the lighttransmission path. The single elongated hole has the elongationgenerally aligned with axis 19C.

Referring now to FIG. 1C, thereshown is a side view of the patientinterface 10 with adhesive 32 and liner 34. In operation it is desirablefor the patient interface to adhere to the patient. Adhesive 34 may bean entire layer, a pattern (such as dots of adhesive), lines of adhesiveor virtually any other method of distributing adhesive on the patientsurface 22. The adhesive itself is generally chosen so that it iscompatible with human tissue and does not create a permanent bond. Oneadhesive that may be used is 3M 1524 adhesive. Other adhesives havinghypoallergenic properties would also be acceptable. Alternatively,belts, tape, Velcro® fasteners and gloves as well as other well knownattachment methods may be used. The liner 34 covers the adhesive untilthe patient interface is ready for affixing. It is made of a materialthat will lightly adhere to the adhesive, but is easy to remove at thepoint that the patient interface is ready to be used.

As can be seen in FIG. 1D, the liner 34 may be split into two pieces 34Aand 34B. This allows for the liner to be removed in two steps withoutlifting the interface completely off the patient. Other arrangementswhere something other than an even split between the liner pieces may beused as well. In FIG. 1E, the liner is shown as a single piece 34 thatcovers the entire patient side of the interface.

Referring now to FIGS. 2A-B thereshown are top and bottom views of asecond embodiment of the patient interface 10A. This patient interfaceis essentially the same as the patient interface of FIG. 1 except thatit includes an additional wing 13A. The reason for the additional wingwill become apparent in connection with the discussion of FIGS. 5A-D.

The patient interface may be made of a soft polymer material such asSantoprene available from Exxon Mobile Chemicals, CPU-150 available fromStafford Textiles Ltd. Rubber, foam, urethane covered polyester knit andother soft, pliable materials may also be used. The interfaces may beformed by through injection molding. Alternatively, the patientinterface may be formed in an upper and lower piece and ultrasonicallywelded together.

Switching now to the method of placement of the patient interface, aflowchart of two such methods is shown in FIGS. 4A and B. Referring nowto FIG. 4A, it is desirable to locate the patient interface at alocation having a predetermined Tissue Hemoglobin Index (THI)measurement. This will provide a suitable location from which to measurehemoglobin oxygenation. In one case, a local maximum THI value is soughtand the patient interface is moved while the output of the spectrometeris monitored. The user then locates the interface in a positionproviding a highest reading. In an alternative process, a minimumthreshold level of THI is sought by moving the interface. Once theminimum threshold has been found, the interface is attached to thepatient. In one embodiment, the minimum threshold is a two percenttissue hematocrit value

The process for locating the interface using THI measurements includesstarting at block 405, and moving to block 410 where a patientinterface, connected to a tissue spectrometer, is put into a firstposition. Then at block 415, a THI measurement is taken. In block 420,the user determines whether any further locations need to be tested.Such a determination may be made using the above noted minimum thresholdTHI method or the maximum THI method.

If more THI values are needed, then, the patient interface is moved to anew position in block 425 and a new THI measurement is taken again inblock 415. If a new measurement is not needed, then the patientinterface can be held in place while the liner is removed and thepatient interface is adhered to the patient as specified in block 430.The process would then end at block 440.

Alternatively, a higher localized temperature may also be sensed toprovide an indication of the amount of blood flow through a portion oftissue in place of a THI value. In this instance, a temperature sensorwould be mounted in the interface and the interface would be moved untila local maximum temperature is found and then the interface would beattached at the location of the local maximum temperature. Other sensorsthat may indicate a local maximum of blood flow may be used. The key isthat it is preferable to place the interface where a local maximum ofblood flow may occur and that the sensing method used for placementprovide some indication of local blood flow.

Alternatively, the locating feature of the patient interface may be usedwithout a blood flow measurement to aid in placement the patientinterface as shown in FIG. 4B. After starting at block 450, the processmoves to block 460 where the alignment guide of the patient interface isplaced in a desired location (such as the base of a finger). Next, theopposite end of the patient interface is located so that an axis runningthrough the midpoint of the patient locating feature and the oppositeend is aligned with a muscle to be monitored as described in block 470.The liner is then removed as in block 480 and the interface is affixedto the patient in 490 before the process ends in block 495.

There are at least three ways of removing the liner as described inblock 430. First, a single liner may be used. Once the location havingthe desired THI value is located, the patient interface may be tilted toone side at the desired location and the single liner removed. Thepatient interface may then be placed back onto the patient. In the casewhere a split liner is used, the patient interface may be placed at thelocation having the desired THI value and the patient interface ispartially lifted so that one side of the split liner may be removed. Thepatient interface is then replaced on the patient so that the adhesivethat has been uncovered attaches to the patient. The other side of thepatient interface may then be lifted and the liner removed and thelifted portion is again replaced on the patient. Lastly, a “butterfly”liner may be used (as described herein) for removal of the liner withoutlifting of the patient interface.

THI may be calculated using the process specified in U.S. Pat. No.6,473,632 (“Myers”) commonly assigned with the present patent. By usingthe combination of both a single term ratio of a second derivative lightabsorbance value of tissue and a single term non-ratioed secondderivative light absorbance value of the tissue, measure of the volumepercentage of a chromophore such as hemoglobin in tissue (a value thatdirectly correlates with hemoglobin concentration) can be calculated(the above noted THI).

In one configuration the wavelength gap used to calculate the secondderivative values (i.e., the interval between adjacent absorbancewavelengths used in the second derivative calculation) is 40 nm. At thisgap size only four wavelengths are used to calculate both the percentageof oxidized hemoglobin and the THI. The second derivative absorbancepeak at 720 nm (deoxyhemoglobin absorption band of 760 nm) is used toempirically derive the relationship between THI and second derivativeabsorbance. Second derivative gap sizes other than 40 nm can also beused to derive the hematocrit algorithm. Also, other wavelength regions(e.g., visible or infrared) corresponding to other oxyhemoglobin ordeoxyhemoglobin absorbance maximums could be used.

The THI measurements made in accordance with the algorithms describedherein can be used by an instrument in connection with tissuerecognition algorithms. Inaccurate and/or invalid measurements of % StO2or other measured parameters can be displayed by the instrument monitorif the probe is not properly located on the tissue to be measured. TheTHI can be used by the instrument to determine whether the probe isproperly positioned and the measurement is accurate. For example, inconnection with some or all of the parameter measurements, theinstrument can compute the THI using the algorithm described herein, anddisplay the parameter measurement as an accurate measurement only if theTHI is representative of a predetermined minimum level. If the THI isbelow the predetermined level, the monitor can generate a displayindicating that the probe is not properly positioned.

THI measurements can be generated as a function of current secondderivative spectroscopy values and stored data describing therelationship between the second derivative values and the tissuehemoglobin concentration. In the embodiment described below, the storedrelationship data is data describing a set of lines or slopes (or curvesif preferred), each of which is associated with a constant oxidationstate of hemoglobin.

During THI, the proper stored relationship data can be selected by theinstrument on the basis of the measured hemoglobin oxidation state. Fromthis data and the current second derivative spectroscopy value, the THIcan be computed by the instrument.

At multiple levels of hematocrit (HCT), the second derivative spectralfeatures of the blood are recorded at a predetermined (e.g., 5 mm) probespacing over multiple % StO2 values within the 0%-100% range. For eachhematocrit the 720 nm second derivative peak is fitted to a linearequation.

At each constant level of % StO2, the second derivative 720 nm featureis related to % hematocrit with extrapolation to 0% hematocrit. There isa linear relationship between the 720 nm second derivative andhematocrit at hematocrits of about 25% and less.

Using linear extrapolation to 0% hematocrit and empirical measurementsat 25% and 15% hematocrit, a lookup table of relationship data whichdescribes the sensitivity of hematocrit to the 720 nm second derivativevalues (lines of constant % StO2) can be created. The slopes arefunctionally related to the ratio of the second derivative at 680 nm tothe second derivative at 720 nm.

The stored relationship data described above is subsequently used duringtissue hemoglobin concentration measurements. Upon measuring % StO2(e.g., using conventional algorithms and scaled second derivative valuesat 680 nm) the corresponding slope value (Mso2 or HCT slope) is foundwithin the lookup table. The predicted hematocrit value is then:% HCT=(Mso2)×(D720/PSF)Where: D720 is the second derivative at 720 nm using the 40 nm gap PSFis the relative path length change due to probe spacing.

The concentration of tissue hematocrit is generally less than 25%, andis usually in the 1%-10% range. When evaluating probe position on thebasis of hemoglobin concentration measurements, relatively highmeasurement accuracy near the lower end of the range is sufficient. Forexample, the threshold for determining whether the probe is on or offtissue can be in the range of 1% measured hemoglobin concentration. Thelinear range of spectral features versus hematocrit concentration needonly be used for this application. However, in accordance with thepresent invention, the measurement accuracy can be extended to greaterpercentages of hematocrit by redefining the algorithm to account fornonlinearities. The algorithm could, for example, be redefined as amultiple regression algorithm consisting of multiple slope and secondderivative transformations (linear transformations). Examples ofnonlinear equations include:% HCT=(Mso2₁)×(D720/PSF)+(Mso2₂)×Log(D720/PSF)or%HCT=(Mso2₁)×(D720/PSF)+(Mso2₂)×(D720/PSF)^(1/2)+(Mso2₃)×(D720/PSF)^(1/3)+. . .Where: Mso2₁, Mso2₂, . . . are nonlinear slope value coefficients whichcan be stored in the lookup table.

The probe scaling factor (PSF) can be empirically determined bycollecting second derivative spectral measurements of a chromophoremedium, preferably having constant scattering and absorption properties,with optical probes having variable distances between the optical sendand receive fibers. The spectral measurements at each probe spacing arethen referenced (ratioed) to one of the fixed probe spacing spectralmeasurements at a particular wavelength of interest. The ratio of onesecond derivative spectrum value at a probe spacing of interest to thesecond derivative spectrum value of the reference probe spacing thenreflects the probe scaling factor. The probe scaling factor can bedetermined at calibration stored in memory.

Referring now to FIGS. 3A-C, thereshown is a patient interface as usedin the process of FIGS. 4A-B. In FIG. 3A, the patient interface 15 isshown in a first position X such that concave region 16 would lieproximal to the thumb by some amount. Note that wings 13 and 14 are notpermanently set around the thumb at this point. A significant portion ofthe base 12 would cover the thenar eminence 315. A THI measurement wouldbe made at this location. Then, the patient interface may be moved, forexample, to the location indicated as Y in FIG. 3B. Here, not only isthe concave region 16 over the thumb, so is a portion of the base 12.Little of the base 12 is covering the thenar eminence 315. Another THImeasurement would be made here. Then, if the THI measurement at locationY is more desirable the THI measurement at location X, the value atposition Y would be stored or otherwise noted (or if this was deemed tobe a final test location, the patient interface 10 could be fixed atthis location). In our case, we wish to try one more location.

As shown in FIG. 3C, a location Z between locations X and Y is thenselected. Here, if a desired THI value is found (we will assume it is)it replaces the previous THI value and if this is the final location tobe tested (we will again assume that it is) the patient interface maythen be removably affixed to the patient by, for example, removal of theliner (not shown in this figure) and placement of the adhesive onto thetissue. Note that wings 13 and 14 are wrapped partly around the thumb.In a particularly preferred embodiment, the wings are not long enough towrap entirely around the thumb.

Referring now to FIGS. 5A-D thereshown are alternate locations for thepatient interface shown in FIGS. 2A-B. The process followed to place thepatient interface here may parallel the process specified in FIGS. 4A-B.In FIGS. 5A-B, the measurement site selected is the first dorsalinterosseous. The concave region 16 is located at a side of the indexfinger distal to the junction of the finger with the hand. The firstwing 13 and additional wing 13A are wrapped around between the indexfinger and thumb on the back side of the hand while the second wing 14is wrapped around between the index finger and the middle finger on theback side of the hand (see particularly FIG. 5B). The second wing isparticularly useful in maintaining a stable attachment to the hand inthis location. The second wing is also helpful in blocking ambientlight. In FIG. 5C, the concave region 16 is located at the junction ofthe finger with the hand. Wings 13 and 13A extend between the indexfinger and the thumb onto the palm as shown in FIG. 5D. Wing 14 maypreferably extend in the direction of the middle finger, or wrap aroundbetween the index and middle finger.

Referring now to FIGS. 7A-B, thereshown are top and bottom views of yetanother embodiment of the patient interface of the present invention.The patient interface 100 includes base 12, wings 13 and 14, convexregions 15A and B, concave region 16, pocket 18 and opening 20. Here,unlike the patient interface of FIG. 1, the base 12 does not have asemi-circular portion between convex regions 15A and 15B. Instead, theconvex regions are formed similar to the wings 13 and 14. The convexregions 15A and B lead into concave regions 17A and B. By having theseparate convex regions and wings, this embodiment of the patientinterface is well adapted to mounting on a location where the diameterof the body part on which the patient interface may change from one endof the patient interface to the other. In particular, this interface maybe used for measurement of an adult deltoid muscle. Wings 13 and 14 arewell adapted to partially wrap around the arm. Concave region 16 servesas a locating feature such as at the junction of the arm with theshoulder. Other locating features such as v shapes or notches are alsocontemplated.

FIG. 6A shows yet another placement of the patient interface of FIG. 1.Here, the patient interface is placed along an axis under which theadductor pollicis muscle runs. The patient interface 10 is placed in alocation such that one wing contacts the junction of the thumb with thehand while the other wing contacts the junction of the forefinger withthe hand. FIG. 6B shows placement of the patient interface of FIGS. 7A-Balong the adductor pollicis muscle. For both FIGS. 6A-B, the base of thepatient interface is then placed so that the holes 23 and 24 are alignedalong the adductor pollicis muscle.

A common theme among all of the placements is a desire to align theholes 23 and 24 along a longitudinal axis of the muscle. This is aprimary reason for having the concave region and wings as shown. Thisalignment produces a significant signal path for the light to transversethrough perfused tissue. Each finger has a muscle known as the lumbricalmuscles running axially from the heel of the hand to the junction of thefinger with the palm. Each such muscle presents an acceptable site alongwhich the patient interface may be placed. The wings may be extendedaround the side of a finger with the opposite end of the patientinterface (particularly where the opening 20 is located) beingpositioned generally in alignment with the finger around which the wingshave been placed.

Referring now to FIGS. 8A-B, thereshown are two additional interfacedesigns. In FIG. 8A, an interface 10 similar to the interface of FIG. 1is shown. Here, however, an optical head may be inserted into opening200 so that the interface may be left in place at a desired locationwhile allowing for the option of removal of the spectrometer if sodesired. An alternative design is shown in FIG. 8B.

Referring now to FIGS. 9A-B, thereshown are other alternative locationsfor an interface on a hand. Two preferred locations include the back ofthe hand on the webspace between the thumb and forefinger (the firstdorsal interosseous) (FIG. 9A) and on the hypothenar muscle (FIG. 9B).

In FIGS. 11A and B, thereshown is a “butterfly” version of the liner onthe patient interface 10. The base 12 of the patient interface may beformed with a central opening 200 therein. An adhesive (not shown) maybe placed on a patient facing portion of the patient interface tofacilitate mounting the patient interface on the patient. Split liner 34may be placed on the adhesive to prevent the patient interface fromattaching to anything other than the patient. As can be seen moreparticularly in FIG. 11B, the split liner may be a folded or hinged, at34C and D, piece of material that includes a patient side 34A and B andan adhesive side 34AA and BB. To use an interface having the butterflyversion of the liner, the interface is lightly placed on the patient ata desired location. While holding the interface in place, tabs 35A and Bare then pulled, in a direction normal to axis 19A-B and substantiallycoplanar with the plane in which sides 34A and B reside. The liner 34will then move as indicated by arrows X and Y such that adhesive on theinterface is then exposed and placed in contact with the patient as theliner is removed.

Referring now to FIGS. 12 and 13 is another embodiment of the invention.In this embodiment, the present invention is a butterfly shaped patientinterface as is shown in FIGS. 12-18. The patient interface may be anadhesive coated fabric skirt. The butterfly shape is generally symmetricabout a central axis such that it is ambidextrous, i.e., may beinstalled on both left hands and right hands. The size of the patientinterface is selected to fit approximately 95% of the adult population.Preferably, the patient interface extends a minimum 1 inch radius abouta receive fiber that is part of the optical head. The optical head islocated on top of the patient interface and generally in a centralregion of the patient interface. In some embodiments, a cap or islandcovers or houses the optical head to provide increased light blockingcharacteristics to the patient interface. The cap or island may be madeup of rubber, foam or any other material that will provide increasedlight blocking characteristics. The cap or island may be removable. Theskirt or wing portion of the patient interface may be made of materialsthat provide breathability, or transmit moisture vapor, providesconsistent reflection against the skin surface, and blocks ambientlight. In one embodiment the patient interface is made of material suchas CPU-150. In one embodiment, the adhesive may be a full surfacecoating, in other embodiments, it may be any partial or patternedcoating. The adhesive may be covered with a split liner. In oneembodiment, the split liner and base material are made of a spectrallyflat material that will not induce a spectral shift and minimizesreflection. An example of such spectrally flat material is CPU-150.

In another embodiment, the present invention is a method of installing apatient interface for a spectroscopy kit on a patient. Prior toinstalling the patient interface on the skin surface, a barrier film,such as 3M Cavilon®, may be applied to enhance the effectiveness of theadhesive. Preferably, the barrier film does not affect the reflection oflight against the skin surface. Once the patient interface is affixed tothe patient, the patient interface is connected to a monitor of aspectrometer via a cable. One end of a cable is connected to the opticalhead and the other end of the cable is connected to a monitor.

All publications, patent applications and patents identified in thisdescription are incorporated by reference as if they were fully set outherein.

1. A patient interface for a tissue measurement instrument, the patientinterface comprising: a flexible base member having a central regionwith a longitudinal axis, the base member having an outer perimeterdefining a distal concave locating feature, the outer perimeter furtherdefining a pair of opposing wings extending from the central region ofthe base member, each wing having a convex outer perimeter, the wingsgenerally symmetric about the longitudinal axis, the longitudinal axissubstantially bisecting the locating feature; wherein the base memberhas two openings for light transmission therethrough, the openings lyinggenerally along the longitudinal axis and defining a sensor region ofthe central region; wherein the wings extend longitudinally along theouter perimeter of the base member adjacent the sensor region; and anopaque cap positioned on the central region of the base member and inproximity to an optical head.
 2. The patient interface of claim 1further comprising an adhesive coating on an underside of the patientinterface.
 3. The patient interface of claim 2 further comprising abifurcated release liner covering the adhesive coating.
 4. The patientinterface of claim 3 wherein the release liner covering is made of aspectrally flat material that minimizes light reflection.
 5. The patientinterface of claim 1 further comprising a connector and cable.
 6. Thepatient interface of claim 1 wherein the base member and wings comprisematerials that breathe, transmit moisture vapor, block ambient light ora combination thereof.
 7. The patient interface of claim 1 wherein thecap is a foam cap.
 8. The patient interface of claim 7 wherein the capis removable.
 9. The patient interface of claim 1 wherein the base andwings are removable.
 10. The patient interface of claim 1 wherein basemember is made of a spectrally flat material that minimizes lightreflection.
 11. A method of installing a patient interface for a tissuemeasurement instrument comprising the steps of: providing a flexiblebase member having a central region with a longitudinal axis, the basemember having an outer perimeter defining a distal concave locatingfeature, the outer perimeter further defining a pair of opposing wingsextending from the central region of the base member, the wingsgenerally symmetric about the longitudinal axis, the base member havingone or more openings for light transmission therethrough, the one ormore openings lying generally along the longitudinal axis and defining asensor portion of the central region, wherein the wings extendlongitudinally along the outer perimeter of the base member adjacent thesensor portion; and a cap positioned on the central region of the basemember and surrounding an optical head; connecting one end of a cable tothe optical head and the other end of the cable to a monitor; andaffixing the patient interface onto a patient.
 12. The method of claim11 further comprising applying on skin of the patient an adhesiveenhancer prior to affixing the patient interface.
 13. The method ofclaim 12 wherein the adhesive enhancer is a barrier film.
 14. Thepatient interface of claim 11, wherein the wings form a convex portionof the outer perimeter.
 15. A patient interface for a tissue measurementinstrument, the patient interface comprising: a flexible base memberhaving a central region along a longitudinal axis, the base memberhaving an outer perimeter defining a distal concave locating feature,the outer perimeter further defining a pair of opposing wings extendingfrom the central region, the wings generally symmetric about thelongitudinal axis; the base member having one or more openings for lighttransmission therethrough, the one or more openings lying generallyalong the longitudinal axis and defining a sensor portion of the centralregion, wherein the wings extend longitudinally along the outerperimeter adjacent the sensor portion; and a cap positioned on thecentral region of the base member and in proximity to an optical head.16. The patient interface of claim 15 wherein the patient interface hasa top and bottom side, the bottom side being adapted to be placed incontact with a patient, and further comprising: an adhesive located onthe bottom side; and a first liner covering the adhesive.
 17. Thepatient interface of claim 15 further comprising a second liner suchthat the first liner covers a portion of the adhesive while the secondliner covers another portion of the adhesive.
 18. The patient interfaceof claim 15 wherein the base member, wings and cap are removable. 19.The patient interface of claim 15 wherein the base member and wingscomprise materials that breathe, transmit moisture vapor, block ambientlight or a combination thereof.
 20. The patient interface of claim 15,wherein the wings form a convex portion of the outer perimeter.